The Syrian opposition's chief negotiator in peace talks in Geneva said on Wednesday he was "not optimistic" about strained efforts to end the nearly five-year war ravaging his country. Mohammed Alloush, a leading member of the Army of Islam rebel group, told journalists that those pressing to form a unity government with regime members were "delusional." "Whoever wants us to go into a unity government with these thugs who kill children is delusional," he said, minutes before heading into a meeting with the main opposition grouping, the High Negotiations Committee (HNC). The HNC was in internal talks on Wednesday morning to discuss its next steps, after a similar and tense meeting the previous evening, an opposition source said. Asked what the grouping would discuss, Alloush clutched a picture of a young boy who he said had been severely wounded by Russian air strikes in Syria. "The problem is not with (UN envoy Staffan) de Mistura. The problem is with the criminal regime that decimates children and with Russia which always tries to stand alongside criminals," Alloush said. He told reporters the HNC would be taking a decision "in two days" but did not specify what that decision was. HNC head and former Syrian prime minister Riad Hijab is set to arrive in Switzerland on Wednesday, an HNC spokesman said, in a potential sign of fresh momentum after talks faltered on Tuesday. The expected arrival of High Negotiations Committee (HNC) general coordinator Hijab comes as the biggest diplomatic push to date to end the almost five-year-old war hangs by a thread, with formal talks yet to begin in earnest. Hijab was chosen in December as general coordinator of the HNC.